logged stand of trees. 21. Lltterial data from (S), ndcate that t t e r f a lnputs of carbon are between about 50 and 120 g m-'year-' for coniferous forests of the Slerra transect above 1200 m eevaton We estimated carbon productivity for grasses at the Fabrook slte by assumng that ther v a l~~e s are smlar to those for other grassland soils In Cafornla (between 50 and 100 g m-' y e a r 1 [R. Vaentn et a1 , Ecology 76 1940 (1 995)] 22 D. C. Nepstad e i a/. , i~laiure 372 666 (I 994) 23 S E Trumbore er a1 , Global Biogeochem Cycles 9. 515 (1995). 24. W M Post era/., Nature 298, 156 (1 982); D. S. Jenklnson, D E Adams, A. W11d /bid 351,304 (1991), A. R. Townsend eta/., Chm Change 22, 293 (1992). 25. M. Klrschba~lm So11 Blol. Biochem. 27, 753 (1 995). 26. The est~mates of carbon change In Fig. 3 Ignore important factors, such as probable changes n carbon inputs to the soil by plants and feedbacks be-tween SOM decomposton and plant productivity, In additlon the climate transects studled ~n H a w a and the Serra Nevada Integrate long-term adj~~stment of ecosystems to average cllmatic cond~t~ons, and translent responses may not be predctabe from the temperature-turnover relations derlved here However, soil incubations and sol respratlon measurements have shown that on short t m e scales, carbon fluxes from soils are strongly dependent on temperature, with Ql , values ranglng from 2 to 5 [J. W. Rach and W. H. Schesnger, Tellus 448, 81 (1 992); D W. Klckghter er a/., J. Geophys Res. 99, 1303 (1 994)] (25) In accord with values, derlved from F g 2, of 3 0 to 3 8. [Q,, 1s the rateoia b i o o g c a process (here, decompositon) at one temperatwe divded by the rate of the process at a temperature 10°C cooler ] 27.

Europium activated yttrium oxide (Eu:Y2O3) phosphor films have been grown in situ on (100) bare and diamond-coated silicon substrates using a pulsed laser deposition technique. Diamond-coated silicon substrates were prepared using hot filament chemical vapor deposition of diamond onto silicon. Photoluminescence brightness from Eu:Y2O3 films grown at 700 °C on diamond-coated silicon substrates was about twice that of films on bare silicon, and reached 80% of the brightness of powders. The higher brightness from Eu:Y2O3 film on diamond-coated silicon substrates is attributed to reduced internal reflections from the Eu:Y2O3 film surface, which results from the roughness of the diamond layer.

To integrate irreconcilable material properties into a single component, novel engineered materials termed ‘surface composites’ have been developed. In these engineered materials, the second phase is spatially distributed in the near surface region, whereas the phase composition is linearly graded as a function of distance from the surface. Surface composites are different from existing engineered materials such as bulk composites and functionally graded materials (FGM). Unlike in bulk composites, the surface phase in surface composites is present only in the near surface region. In contrast to FGMs, the graded properties of surface composites are achieved by unique morphological surface modification of the bulk phase. To fabricate surface composites, the initial surface of the bulk material is transformed using a novel multiple pulse irradiation technique into truncated conelike structures. The laser induced microrough structures possess surface areas which are up to an order of magnitude higher than that of the original sUljace. The second phase is deposited on the surface using thin or thick film deposition methods. A key characteristic of surface composites is the formation of a three-dimensional, compositonally and thermallygraded interface, which gives rise to improved adhesion of the surface phase. Examples of various types of surface composites such as W/Mo and diamond/WC–Co are presented. The unique properties of surface composites make them ideal engineered materials for applications involving adherent thick film coatings of thermally mismatched materials, compositional surface modification for controlled catalytic activity, and creating adherent metal–ceramic and ceramic–polymer joints.

Europium-activated yttrium oxide (Eu:Y203) phosphor films have been grown in situ on (100) bare silicon and diamond-coated silicon substrates using a pulsed laser deposition technique. Diamond-coated silicon substrates were prepared by hot filament chemical vapor deposition onto (100) silicon wafers. Measurements of photoluminescence and cathodoluminescence properties of Eu:Y203 films have shown that the films grown on diamond-coated silicon substrates are brighter than the films grown on bare silicon substrates under identical deposition conditions. The improved brightness of the Eu:Y202 films on diamond-coated silicon substrates is attributed to reduced internal reflection, low photon energy absorption by substrate, and enhanced scattering of incident beam with lattice. All these effects are primarily brought about by the presence of a rough diamond interfacial layer between the phosphor films and substrates.

Growth and Characterization of Eu:Y 2 O 3 Thin-Film Phosphors on Silicon and Diamond-Coated Silicon Substrates.-High quality phosphor films are deposited by use of the pulsed laser deposition technique. The highest brightness obtained for as-deposited Eu:Y 2 O 3 films grown on diamond-coated Si substrates at 700 • C is comparable to the brightness of Eu:Y 2 O 3 powder. This can be attributed to reduced internal reflection, low photon energy absorption by substrate, and enhanced scattering of incident beam with lattice. -(CHO, K. G.; KUMAR, D.; JONES, S. L.; LEE, D. G.; HOLLOWAY, P. H.; SINGH, R. K.; J. Electrochem. Soc. 145 (1998) 10, 3456-3462; Dep. Mater. Sci. Eng., Univ. Fla.,